COMMERCIAL FERTILIZERS 521 



experiments as arising from the different kinds of fer- 

 mentation that the organic matter undergoes. He thinks 

 that acid fermentation renders the phosphate more readily 

 soluble, while fermentation that does not give rise to acids 

 leaves it in an insoluble condition. 



Parallel with the biological process that results in the 

 transformation of insoluble phosphates into soluble, there 

 is, according to Stoklasa and others, a reverse biological 

 process resulting in the transformation of soluble phos- 

 phates into insoluble. 



Whatever may be the conditions under which raw rock 

 phosphate is rendered more readily soluble or available 

 by fermentation of organic matter, it does not appear 

 that composting with stable manure produces this change, 

 at least from results of numerous experiments including 

 those mentioned above. These have been mainly opposed 

 to any such conclusion. 



440. Influence of other salts. — The presence of cer- 

 tain salts has been found to influence the availability of 

 difficultly soluble phosphates. The subject has been in- 

 vestigated by a large number of experimenters and it will 

 be possible to summarize their results only in part and 

 very briefly. It has been found, for instance, that cal- 

 cium carbonate decreases the availability of raw rock 

 phosphate and bone-meal. Sodium nitrate reduces the 

 availability of the tricalcium phosphates, while the am- 

 monium salts increase their availability. Iron salts 

 decrease availability. The influence of other salts has not 

 been so well worked out. Prianischnikov, 1 as the result 

 of his extended experiments on the subject, holds that 



1 Prianischnikov, D. Ueber den Einfluss von Kohlensiinren 

 Kalk auf die Wirkung von Verschiedenen Phosphaten. Landw. 

 Vers. Stat., Band 75, Seite 357-376. 1911. 



